Tripod Dolly with suspension

I wanted a way too shoot dolly like footage.
I saw these wheels for tripod online but they all had very small wheels and no suspension.

So I designed something, it was some time ago, if something is unclear, please ask.

the bolts are wood bolts with a rounded head and a square part.
I got the springs from rsonline, they may be a bit too stiff.
A bit of oil is required for a smooth suspension.

Steering is a bit akward and requires some practice ;-)

See it in action:
https://youtu.be/qcyc2sVfink

List of materials (99% sure):
Tubes are 25.4mm diameter, I use 4130 tubes from ceeway.
Length depend how big you make it, at least 3x50cm is needed I would say.
Wood bolts (round head with square piece) - M8 x 140mm
4x M8 locknut for those wood bolts + 4xm8 washer

16x M10 washer or similar between to cover both spring ends so the spring is seperated from the plastic, add more for increased spring tension.
the springs I used are from rsonline, part number 751-607
RS Pro Steel Alloy Compression Spring, 26mm x 11mm, 1.85N/mm

12xM5x35 + M5 nut + M5 washer to mount the tubes to the weel frame

6x M5x45 + 12 washers + 6 locknuts to mount the wheel arms

the wheels + bearings are:
3x hyper formula hockey wheels - 80mm 76A
6x supreme abec 7 bearing
3x axle
3x spacer
I order this here:
3x https://www.skatepro.nl/40-594.htm
6x https://www.skatepro.nl/27-1617.htm
3x https://www.skatepro.nl/297-12784.htm
3x https://www.skatepro.nl/37-3890.htm

larger wheels could be done with minor modifications